Zeolites have numerous industrial applications, and zeolites having an AEI framework are known to be effective catalysts for treating internal combustion exhaust gases, for selective catalytic reduction of NOx in exhaust gases, and, e.g., for methanol-to-olefin conversion. Of particular interest is SSZ-39 zeolite. Zeolites such as SSZ-39 are made with organic structure-directing agents (OSDAs), sometimes referred to as templates, which are usually organic bases which guide or direct the molecular shape and pattern of the zeolite framework. The OSDAs act something like a frame around which the zeolite crystals form, and following the formation of the crystals, the OSDA is removed, leaving a porous aluminosilicate structure.
One of the most commonly used ammonium based OSDAs for making SSZ-39 is N,N-dimethyl-3,5-dimethylpiperidinium cation, which is usually provided as the hydroxide in the synthesis of SSZ-39, which herein is referred to as “PIPPY”. PIPPY is also sometimes referred to as 1,1,3,5-tetramethylpiperidinium cation, usually provided as the hydroxide.
An ongoing problem that continues to exist in conventional processes for making AEI framework zeolites, particularly SSZ-39 zeolites, is that the morphology of the zeolite crystals produced may not be optimum for some catalytic applications, for example, the crystals may be, on one hand, too thick or too big, or on the other hand, too small and/or too easily packed too tightly to be efficiently used in catalytic applications. In other cases, the surface area to volume ratio may be too small, which results in many of the inner pores being inaccessible to the reaction components. The resulting low activity inevitably raises the cost of using the catalyst.